In general, in the field of dentistry, using a dental X-ray imaging system for dental treatment or orthodontics, various imaging methods have been utilized, for instance, a panoramic radiography image scanning of the entire structure of teeth and the alveolar bone, a cephalometric image scanning of areas ranging from the front to the rear and ranging from the rear to the front of a patient's head and jawbone, and of the left side and the right side of the patient's head and jawbone, and a method of imaging the patient's oral cavity by irradiating a narrow x-ray beam to the patient's oral cavity from the outside after inserting a small sensor (intraoral sensor) for receiving the x-ray beam.
The panoramic image allows a user to observe the whole areas of the teeth and the alveolar bone in plane, but has a problem in that it is difficult to distinguish a minute forward or backward inclination of the teeth or a partial malocclusion in teeth arrangement. The cephalometric images can make up for the weak points of the panoramic images, but has a problem in that it is impossible to grasp the whole areas of the teeth and the jawbone at once.
So, since the panoramic image and the cephalometric image are simultaneously utilized because of their complementary features, the tendency is toward an increase in using a dental x-ray imaging system, that a detector for cephalogram is mounted on a panoramic x-ray imaging system to thereby scan the cephalometric image using the panoramic x-ray imaging system.
In the meantime, the panoramic image and the cephalometric image use 2-dimensional projection data. So, they generate an image-overlapping phenomenon because of a simple 2-dimensional projection image, and so, cause a difficulty in diagnosis of dental diseases. Recently, a 3-dimensional computed tomography (CT) imaging system has been developed and spread.
The dental CT imaging is to obtain a tomographic image of the inside of a thing to be scaned by mathematically reconstructing projection data of several tens to several hundreds around the thing using a computer.